1. Field of the Invention
The present invention relates to a developing treatment method and a developing treatment unit for a substrate.
2. Description of the Related Art
In photolithography of the process of fabricating a semiconductor device, for example, resist coating treatment for coating the surface of a wafer with a resist solution to form a resist film thereon, exposure processing for exposing a pattern on the wafer, developing treatment for developing the exposed wafer, and the like are performed in sequence to form a predetermined circuit pattern on the wafer.
In the aforesaid developing treatment, usually a developing solution supply nozzle which is formed longer than a diameter of the wafer and has a plurality of supply ports along its longitudinal direction moves from one end to the other end of the wafer while discharging a developing solution onto the wafer, whereby the developing solution is supplied to the entire surface of the wafer. After a developing solution film is formed on the wafer, the wafer is developed while remaining stationary in that state for a predetermined period of time. On this occasion, on the wafer, a resist film and the developing solution at an exposed portion which becomes soluble in the developing solution by exposure chemically react with each other to dissolve the exposed portion, whereby the developing of the wafer progresses.
However, it is found by experiment by the inventor, et al. that when the developing solution supply nozzle supplies the developing solution while moving in a predetermined direction as described above, there occurs a so-called flow phenomenon of the developing solution, in which the supplied developing solution flows in a direction opposite to a moving direction of the developing solution supply nozzle, that is, in a direction from the other end to the one end of the wafer.
When the developing solution with a high concentration which is at an unexposed portion and not yet used for a chemical reaction flows into an adjacent exposed portion under such a phenomenon, however, the chemical reaction speed at this exposed portion increases, and hence the developing speed at this portion increases compared with other portions. As a result, a line width at this portion becomes narrower compared with those at other portions.
Meanwhile, when the developing solution with a low concentration which is at an exposed portion and used for a chemical reaction flows into an adjacent exposed portion, the reaction speed at this exposed portion decreases, and hence the developing speed at this portion decreases, whereby a line width at this position becomes wider compared with those at other portions. Specifically, the developing speed within the surface of the wafer becomes ununiform due to the aforesaid phenomenon, which causes unevenness of line width of a circuit pattern finally formed on the wafer.
The present invention is made in view of the aforesaid point, and its object is to provide a developing treatment method and a developing treatment unit for eliminating the ununiformity of developing speed within the surface of a substrate such as a wafer caused by the aforesaid flow phenomenon of a developing solution, finally leading to the formation of uniform line width on the substrate.
The present invention is a method of supplying a developing solution to a surface of a substrate to perform developing treatment for the substrate, comprising: a first step of supplying the developing solution to the surface of the substrate while a developing solution supply nozzle is moving relative to the substrate; and a second step of developing the substrate for a first predetermined period of time, the second step having the step of stirring the developing solution on the surface of the substrate after a second predetermined period of time from the completion of the first step.
The stirring step is performed, for example, by rotating the substrate.
It is desirable that the substrate be rotated so that a thickness of the developing solution after the step of stirring the developing solution is not less than a predetermined thickness. Moreover, the step of measuring a thickness of the developing solution after the step of stirring the developing solution and the step of changing a rotation time of the substrate based on the measurement may be further added. Alternatively, the step of measuring a thickness of the developing solution after the step of stirring the developing solution and the step of changing a rotation speed of the substrate based on the measurement may be further added. Alternatively, the step of measuring a thickness of the developing solution after the step of stirring the developing solution and the step of changing a rotation acceleration of the substrate based on the measurement may be further added.
A developing treatment unit of the present invention is a unit for performing developing treatment for a substrate by supplying a developing solution to a surface of the substrate while moving a developing solution supply nozzle relative to the substrate, comprising: a rotary drive member for holding and rotating the substrate; and a rotation controller for normally and reversely rotating the rotary drive member after the supply of the developing solution.
According to the present invention, even if such a flow phenomenon of the developing solution as described above occurs, by stirring the developing solution on the surface of the substrate during the second step in which the substrate is being developed, both an exposed portion and an unexposed portion are covered with the developing solution with a uniform concentration, whereby the developing speed is made uniform within the surface of the substrate. According to the knowledge of the inventor, et al., reaction products created by the progress of developing are scattered by stirring, whereby the concentration of the developing solution is made uniform.
The above is realized irrespective of pattern spacing. Accordingly, the ununiformity of line width of a circuit pattern finally formed on the substrate is suppressed. The reason why the stirring step is performed after the second predetermined period of time from the completion of the first step is that immediately after the start of developing, the chemical reaction of the developing solution does not progress so much, hence the concentration of the developing solution is the same within the surface of the substrate, and thus stirring at this point hinders developing rather than has an effect on developing. It is desirable that the second predetermined period of time be a period of time from the supply of the developing solution onto the substrate to approximately 50% to 80% progress of the chemical reaction of developing at the exposed portion, and, for example, when the first predetermined period of time is approximately 60 sec., it is desirable that the second predetermined period of time be approximately 3 sec. to 15 sec. from the result of model experiment by the inventor.
If stirring is performed by rotating the substrate, the developing solution on the substrate is moved by centrifugal force and stirred at the same time. Incidentally, it is important to rotate the substrate for an appropriate period of time and at an appropriate rotation speed and rotation acceleration, and especially as for the rotation speed, 100 rpm to 1000 rpm in case of a wafer with the size of 8 in. and 30 rpm to 1000 rpm in case of a wafer with the size of 12 in. are preferable from the result of the model experiment by the inventor. As for the rotation time, approximately two seconds are preferable. Stirring may be performed in other ways, for example, by giving vibration to the substrate.
It is important that the aforesaid rotation of the substrate is performed so that the thickness of the developing solution after the step of stirring the developing solution is not less than a predetermined thickness. This is because if the developing solution on the substrate is excessively cast off due to the rotation of the substrate and the developing solution film becomes too thin, there occurs such a harmful effect that the developing solution dries and thereby developing is not appropriately performed in developing treatment thereafter. The thickness of the developing solution film is adjusted by controlling the rotation time, rotation speed, and rotation acceleration of the substrate. According to an experimental result by the inventor, it is preferable that the thickness is not less than 8 xcexcm.
By measuring the thickness after the completion of the second step and controlling the rotation time, rotation speed, and rotation acceleration, developing treatment can be performed under more appropriate conditions.
In the aforesaid invention, the first step may be performed by supplying the developing solution to the substrate while the developing solution supply nozzle is moving from one end to the other end of the substrate. When the developing solution film is formed on the substrate by such a movement of the developing solution supply nozzle from the one end to the other end of the substrate, the developing solution to be supplied has a speed in a fixed direction with respect to the substrate, whereby the influence of the aforesaid flow phenomenon of the developing solution is exhibited remarkably. Hence, the aforesaid performance of the stirring step during the step of developing the substrate is significant.
In this case, the step of supplying the developing solution again to the surface of the substrate while moving the developing solution supply nozzle this time in an opposite direction, that is, from the other end to the one end of the substrate after stirring may be further provided, which can further enhance the uniformity of developing treatment.
According to the developing treatment unit of the present invention, the aforesaid stirring can be properly performed by normally and reversely rotating the substrate.